Method of converting hydrocarbons



May 17, 1938.

H. C. SCHUTT METHOD OF CONVERTING HYDROCARBONS Filed Oct. 24, 1955 wm NQQ QN Kt@ AMM Patented May 17, 1938 l UNITED STATES `PATENT ori-ICE METHOD F CONVERTING HYDROCARBONS Hermann Claus Schutt, North Tarrytown, N. Y., assigner, by mcsne assignments, to The Pure Oil Company, Chicago, lll., a corporation of Ohio Application October 24, 1935, Serial No. 46,542

11 Claims.

liquid-vapor or vapor phase cracking still opera--v 1 tions, may be converted into heavier hydrocarbons of the aromatic series, under conditions which will result in a high yield of high octane aromatic-containing liquid boiling within the range of the nature of gasoline motor fuel, and

20 minimize the formation of undesirable products such as tar and fixed gases, e. g., methane and ethane.

In general, my process comprises the separation of the mixture to be used as charging stock,

25 as for example, a. gas containing aliphatic Cz, Ca

and C4 hydrocarbon compounds preferably comprising in excess of thirty per cent unsaturates, into fractions respectively more diiicultly polymerizable in accordance with the increased mo- 30 lecular Weight of the unsaturates in successive fractions, subjecting the most diicultly polymerizable fraction, as for example, that containing substantially C3 and C4 unsaturated compounds, to high temperature, high pressure poly- 35 merization conditions most favorable to the production of the maximum yield of desired aromatic hydrocarbons which may be obtained from that particular fraction, separating the aromatic products from the unreacted low boiling hydro- 40 carbons, subjecting the unreacted hydrocarbons,

as for example, the saturated Cs and C4 compounds, to high temperature, low pressure cracking conditions most favorable to the maximum yield of lighten, more easily polymerizable com- 45 pounds, as for example, substantially Cz unsaturated hydrocarbons, separating these lighter, more easily polymerizable compounds as a fraction from the liquid products formed, subjecting this light fraction to high temperature, low pres- 50 sure polymerization `conditions most favorable to the production of the maximum yield of desired aromatic products therefrom, separatingthe liquid products from the lower boiling hydrocarbons, recycling the lower boiling hydrocarbons to the initial separating step and removing stabilized aromatic-containing products of the nature oi motor fuel from the system. Y

In accordance with my invention, I may pass the lighter compounds, as for example, the Cz hydrocarbons of the starting mixture directly to the intermediate cracking step when these form a relatively small percentage of the starting mixture, to convert the C2 saturates to unsaturates for polymerization in the subsequent low pressure polymerization stage. On the other hand, when the percentage of lighter C2 unsaturates in the starting mixture is relatively high, it may be preferable to pass these directly to the low pressure polymerization stage for the production of a maximum yield of desired aromatic products.

I have found that the operating conditions most suitable for eii'ecting polymerization of heavier unsaturates undergoing treatment, e. g., butylene, are not suitable for the polymerization of ethylene since the latter will polymerize much more rapidly under the same temperature-pressure conditions. Hence, I have found it desirable to separate the hydrocarbons according 'to boiling point as a measure of reaction velocity and subject them to separate stages ofl polymerization and most favorable to the velocity constant, or reaction velocity, of each.

I have also found that during the polymerization of the C3 and C4 compounds, a part of the saturates present are converted to lighter unsaturates. The complete conversion of these saturates to C2 unsaturates is best carried out, however, by a subsequent cracking of all or a part of the polymerization reaction products from which the aromatic and other higher boiling products formed during the initial polymerization stage have been substantially removed. The endothermic character of the cracking reaction is such as to permit cracking of the C2, Ca and C4 compounds as a 'group at an average temperature without excessive decomposition of the heavier C4 compounds to coke or tar. I jdo not, therefore, deem it essential that the separation of the C2, Ca and C4 saturates into their respective fractions and cracking of each separately be practiced though such operation would more nearly approach ideal conditions for optimum conversion of the saturates to unsaturates.

Assuming the charging gasto have the following composition, I cool the gas under pressure to substantially separate the C3-C4 compounds as a liquid from the C2 compounds and methane as follows:

Table Mol. per MOL per uoid cent gas 5. s 57. 8 1. 7 n. 2 1l. 7 24. 2 38. 4 4. 5 14. 1. 5 19. 0 8

'I'he liquid fraction containing the Ca--Ci compounds is pumped directly to a heating coil where it is brought up to a temperature sufficient to initiate the exothermic polymerization reaction after'which it is passed to a high pressure, high temperature reaction coil, preferably of larger cross-sectional area than the heating coil, controlled as to temperature, where the polymerization reaction is permitted to take place. The reaction coil may be operated at a mean temperature range of from 1050 F. to 1150 F., preferably at about 1080 F. and at a mean pressure range of 200 lbs/sq. in. gauge to 400 lbs/sq. in. gauge, preferably at about 300 lbs/sq. in. gauge. 'I'he polymerization reaction products withdrawn from the .reaction coil may be quenched to a temperature below approximately 600 F. and preferably about 425 F.. to inhibit the polymerization reaction, the products after fuel oil and tarseparation being cooled and fractionated to recover aromatic and other liquid products formed by the polymerization reaction.

The low boiling compounds such as the Cs--C4 saturates remaining uncondensed are passed to a low pressure, high temperature gas cracking coil primarily for conversion of saturates 'to Cz'unsaturates. 'I'he cracking reaction may be carried out in the heating coil at a temperature range of from 1325o F. to 1600 F., preferably about 1375 F., and at a pressure range of from 25 lbs/sq. in. gauge to 125 lbs./sq. in. gauge, preferably about '15 lbs./sq. in. gauge. The charge to the gas cracking coil, though primarily consisting of the gases remaining uncondensed after separation of the aromatic-containing products formed by the polymerization operation,'may be supplemented by the addition thereto of the uncondensed C2 gases of the initial separating operation and the gases separated during the cooling of the polymerization products for theA removal of tar and fuel oil formed. p Obviously, therewill be some polymerization of the unsaturates present andformed during the`gas cracking operation. These unsaturates, asfor example, the C2 compounds, will form desired aromatic products. 'I'he reaction products withdrawn from the heating coil may be quenched to below active cracking temperature, i. e., to a temperature ranging below approximately 600 F., preferably about 250 F. The tar and fuel oil formed is then separated from the gaseous constituents which are compressed and cooled to condense the desired aromatic products present. 'I'he gases remaining uncondensed contain the Ca unsaturates and form the charge to the low pressure, high temperature polymerization coil. Where the gases remaining uncondensed after llquefaction of thev feed for the first polymerizing coil contain a relatively high percentage of C2 unsaturates, I prefer to charge these gases directly to the low pressure, high temperature polymerization coil rather than to the gas cracking coil as previously described.

The gaseous chargeto the heating coil of the low pressure polymerization stage may be passed thereinto at a pressure of from 150 lbs./sq. in. gauge to 300 lbs/sq. in.gauge, preferably at about 225 iba/sq. in. gauge and rapidly brought up to a temperature sufllcient to initiate the polymerization reaction a'fter which it passes to a reaction coil of greater cross-sectional area than the heating coil, controlled as to temperature. The exothermic polymerization reaction is permitted to go on in the reaction coil which may be maintained at a mean pressure ranging from 15 lbs./sq. in.- gauge to 120 lbs/sq. in. gauge, preferably about 80 lbs/sq. in. gauge, and at a mean temperature ranging from l100 F. to 1300 F., preferably about 1200" F. Following the proper 'time interval for polymerization, the reaction products may then be quenched to a temperature below approximately 600 F., preferably about 325 F. to inhibit'further polymerization. 'I'he products, following the removal of tar and fuel oil formed during the polymerization reaction, is subjected preferably to steps of absorption and rectication for the recovery of unaThe overhead products of the fractionating operation will consist mainly of a mixture of Ca-Ci compoundsl containing from forty per cent to eighty per cent unsaturates and may be condensed under pressure and recycled for subsequent polymerization in the high pressure polymerization coil.

The tar and fuel oil separated from the reaction products of each of the polymerization and cracking operations contain considerable light distillate recoverable by stripping at pressures ranging from 10 lbs./s`q. in. gauge. This liquid is used as a quench medium supplementing that recovered by cooling and condensation of a portion of the quenched reaction products at higher pressures. y

'It is to be understood that the temperatures maintained in the respective reaction coils may be varied according lto the type and amount of hydrocarbons introduced, the pressure under which the respective polymerization and reaction coils may be operated, and the time of exposure of the gases to the operating temperature. In case an extremely high octane number is not desired, the polymerization operations may be conducted at pressures of the order of 400 lbs./sq. in. gauge to 3000 lbs/sq. in. gauge with correspondingly lowerpolymerization temperatures ranging upward from 700 F.

The accompanying drawing which forms part of this specication and is to be read in con- Junction therewith, is a schematic showing of apparatus in accordance withmy invention.

Refinery or pressure still gas may be introduced into the system through pipe I at a pressure of from 250 to 350 lbs/sq. in. gauge, preferably about 300 lbs./sq. in. gauge, partially liquefied in the condenser 2 and passed into a feed tank 3. Assuming the gas charged to comprise mainly Cz, C: and C4 hydrocarbons, the hydrogen present, methane and mainly Cz hydrocarbons may be withdrawn from the tank through the pipe 4 and passed into the light gas feed pipe 5. 'I'he direction of gas flow in this pipe may be selected by suitable manipulation of the pressure control valves 6, 'l and 8 as will be more fully explained hereinafter.

'I'he liquefleld Ca and C4 hydrocarbons in the tankl I may be withdrawn therefrom through the pipe 9 and charged by the pump I0 through the pipe Ilgat a pressure of about 400 lbs/sq. in. gauge to the heating coil I2 of the high pressure polymerization stage where the reactant in passing through the coil is brought up to the desired polymerization temperature. The reactant discharges from the heating coil I2 into the reaction coil I3 Where a mean temperature of about l080 F. and a mean pressure of about 300 lbs/sq. in. gauge may be maintained. The time allowed for passage of the reactant through the coil I3 is sufficient to effect maximum conversion of the Cs-C4 unsaturates to higher boiling aromatic products. On leaving the reaction coil, the reaction products are immediately contacted in the arrester I4 with a cool light quench distillate entering the arrester through the pipe I5 and suddenly cooled to a temperature of about 425 F. to inhibit further polymerization, the quenched products passing from the arrester into a tar separator I5.

'I'he fuel oil and tar separator I5 functions to remove such heavy polymers from the reaction products as are formed during the polymerization reaction, the tar and fuel oil being discharged under the existing pressure through the pipe I1 into the feed pipe I 9 by which the tar is conveyed to a subsequent stripping operation. A valve I8 in the pipe I1 controls the passage of tar into the pipe I9. Bubble plates or other suitable fractionating trays (not shown) and internal reiiuxing in the separator 'ensure sharp separation of the tarry products and the lower boiling hydrocarbons. The uncondensed hydrocarbons may be withdrawn through the pipe 20, pass through a condenser 2l and pipe 22 into the distillate accumulator 23. The distillate accumu lator may be maintained at a pressure of from 215 lbs/sq. in. gauge to 325 lbs/sq. in. gauge, preferably about 275 1bs./sq. in. gauge. Gases may be vented from the accumulator through pipe 23 and control valve 24 .into the light gas feed pipe 5. 'I'he vented gases will be largely Cz hydrocarbons with some methane and hydrogen.

Condensate in the accumulator 23 may be withdrawn through the pipe 25 and pipe 25 by means of the. pumps 21 and 28. The pump 21 returns a portion of its feed as quench distillate through pipe I5 to the arrester I4 and the remainder through pipe 29 to the tar separator as reux. The pump 28 forces its condensate feed through pipe 30, heat exchanger 3i and pipe 32 to primary fractionator 33.

'Ihe fractionator 33 may be operated at a pressure of from 250 lbs./sq. in. gauge to 350 lbs./sq. in. gauge and by means of bubble trays (not shown), refluxing and reboiling of the fractionatory bottoms in reboiler 34, a stabilized aromatic-containing liquid of the nature of motor fuel of to 90 Octane No. CFR. Motor Method is formed. 'I'his liquid, or polymer gasoline. passes from the reboiler 34 through pipe 35, heat exchanger 3l, pipe 35, and cooler 31 into pipe 38 having pressure control valve 39. The polymer gasoline in pipe 38. is combined with other polymer gasoline formed as will be hereinafter shown, to produce a motor fuel of high blending value. i l

The overhead products of the fractionator 33 will consist of ca -C4 saturated compounds which pass through the condenser 45, pipe 4I and into y the reflux accumulator 42. Condensate is withdrawn through the pipe 43 by means of the pump 44 and returned thereby through pipe 45 to the primary fractionator as reflux.

Uncondensed Cri- C4 gases may be vented at the accumulator pressure through pipe 45 andl pressure control valve 41 into the heating coil 48 of thel gas cracking unit. The charge to the gas cracking coil may be supplemented by the C2 gases in pipe 5 which flow therefrom through pipe 43 and pressure reducing valve 50 into pipe 46. Valve 8 in line 5 may be partially or entirely closed.

The reactant in the gas cracking coil may be preferably subjected to a temperature of about 1375 F. at a pressure of 'about 75 lbs./sq. in. gauge so as to form a maximum of C2 unsaturates as Well as such aromatic-containing products of the nature of motor fuel as result from the conversion of C2 unsaturates during the cracking interval. The reaction products discharged from the cracking coil are immediately quenched in arrester 5I toabout 250 F. by cool light distillate from pipe 52, the quenched products passing through pipe 53 into fuel oil and tar separator 54.

The tar separator 54 may be provided with suitable fractionating trays (not shown) and by suitable reiiuxing, a separation of such heavy tar and fuel oil as was formed bythe cracking reaction from the lower boiling hydrocarbons, is eil'ected. The tar separated flows through pipe 55 and pressure reducing valve 55 into feed line I8 for subsequent stripping, `as will be more fully described hereinafter.

'Ihe overhead products of the tar separator 54 pass through pipe 51, condenser 5,8 and pipe 59 into the quench accumulator 58. Due to pressure drop, the accumulator pressure will range from 20 lbs./sq. in. gauge to 120 lbs/sq. in. gauge, preferably about 65 lbs/sq. in. gauge with the resultant formation of but a small quantity of con-a densate. I propose to supplement this condensate with quench distillate recovered from stripping of the tar as will be more fully described hereinafter. Condensate is withdrawn from the accumulator through pipe 8| by pump 62 which returns a portion through pipe 52 as quench distillate to arrester 5I. The remainder is fed through pipe 83 as reflux to the tar separator 54.

Uncondensed low boiling hydrocarbons pass from the accumulator through the pipe 54 to compressor 55 by which they may be compressed to from lbs/sq. in. gauge to 350 lbs/sq. in. gauge, preferably about 250 1bs./sq. in. gauge, and then passed through pipe 88, condenser 61 and pipe 58 into distillate accumulator 59. At the pressure in the accumulator 69 of from 1.50 lbs/sq. in. gauge to 300 lbs/sq. in. gauge, preferably 225 lbs/sq. in. gauge, the uncondensed low boiling hydrocarbons will be mainly Cz compounds, primarily unsaturates formed by the cracking reaction. 'I'he condensate will be aromatics of the nature of motor fuel formed due to such polymerization of C2 unsaturates asj took place in the gas cracking coil 48.

Gaseous C2 hydrocarbons pass from the accumulator 68 through the pipe 10 into heating coil 1| of the relatively low pressure polymerization stage. When the percentage of C2 unsaturates in the gases fed to the system through the pipe is sufliciently high to render immediate polylmerization of these gases feasible, valves 1 and 8 in pipe 5 are closed and valve 6 is opened so that the C2 hydrocarbons withdrawn from the feed tank 3 through the pipe 4 pass through pipe 5 and are commingled with Vgases in pipe 18 passing to the heating coil 1|. l

The reactant may be heated in coil 1| suiliciently to initiate the polymerization reaction and passes into reaction coil 12 where exothermic polymerization may proceed at a mean temperature of about 1200 F. and a mean pressure` of about 80 lbs./sq. in. gauge. The reactant after a time interval suicient to form the desired aromatic-containing products discharges into arrester 13 wherein it is contacted with cool light distillate entering the arrester through pipe 14.

The reaction/products are quenched in the arrester to a temperature of about 325 F. to inhibit the polymerization reaction, the kquenched reaction products passing through pipe 15 into tar and fuel oil separator 16. 1

The tar separator 16 by means of suitable fractionating trays (not shown) and cooling reflux effects a separation of heavy tarry polymers and fuel oil formed from the lower boiling hydrocarbons. The tar separated discharges through pipe 11 and pressure reducing valve 18 into pipe |8 for subsequent tar stripping, as will be more fully described hereinafter.

The uncondensed overhead products of the tar separator pass through pipe 18, condenser 80 and pipe 8| into quench distillate accumulator 82 which may beA maintained under a pressure of from 25 lbs./sq. in. gauge to 100 iba/sq. in. gauge, preferably about 50 lbs/sq. in. gauge, and a temperature of from 100 F to 200 F., preferably about 125 F. In the accumulator 82, a separa-v tion of condensate from the uncondensed hydro-` carbons is made. 'I'he condensate is withdrawn through pipe 83 by'pump 84 and returned thereby through pipe 14 to arrester 13 as quench distillate and through pipe 85 to the separator 15 as reflux. Excess condensate from accumulator 82 may be passed through valve-controlled line 86' and joined with the condensate leaving distillate accumulator 88. The uncondensed hydrocarbons pass from the accumulator 82 through pipe 86,

' cooler 81 and pipe 88 into absorber 88 of an absorption unit.

'I'he gas feed may enter the absorber at a temperaturev of from 60 F. to 100 F., preferably about 80 F., and at a pressure of from 25 lbs./sq. in. gauge to 100 lbs/sq. in. gauge, preferably about 50 iba/sq. in. gauge, and passes through the absorber countercurrent to downflowing lean absorption oil entering the absorber through pipe v 80. The aromatic and other normally liquid products of the nature of motor fuel together with most of the Ca-Ci hydrocarbons which comprise from forty per cent to eighty per cent unsaturates, are removed from the gases by the absorption oil, the residual hydrogen, methane and some C2 hydrocarbons passing ofi' through pipe 8|, pressure reducing valve 82, and pipe 83 into the residual gas pipe 5, in which valve 8 may be partially or entirely closed. s

The rich absorption oil is withdrawn through pipe 84 vby pump 85 and passes through pipe 8,6, heat exchanger 81,pipe 88, preheater 89 and pipe into combined still and rectifier tower |0|. The oil may enter the tower |0| at a pressure of from 250 lbs/sq. in. gauge to 450 lbsr/sq. in. gauge, preferably about 325 lbs/sq. in. gauge, and at a temperature of from 450 F. to 650 F., preferably about 525 F. The absorption oil is stripped with steam entering the tower through pipe |02, the steam condensate formed in the rectifying section of the tower being withdrawn from collecting trays (not shown) through pipe |03. Sharp separation of the absorption oil from the absorbed hydrocarbons is secured by suitable fractionating trays (not shown) in the rectifying section of the tower in conjunction with cool reux entering the tower through the pipe |04. The lean absorption oil is withdrawn through pipe |05 by means of pump |08 and is returned to the absorber 88 through pipe |01, heat exchanger 81, pipe |08, cooler |08 and pipe 80.

The overhead products of the tower |0| pass through pipe H0, condenser and pipe ||2 into separator ||3 where at a pressure of from 245 lbs/sq. in. gauge to 445 lbs./sq. in. gauge, preferably about 320 lbs/sq. in. gauge and a temperature of from 60 F. to 100 F., preferably about 80 F., a separation of some uncondensed C2 hydrocarbons may be effected, these being vented through pipe ||4, pressure control valve ||5, pipe ||6 and pipe 83 into the residue gas pipe 5.

The separator liquid is partly reiiux and discharges from the separator ||3 through pipe I |1, a portion passing through pipe ||8 to pump ||8 and being returned thereby through pipe |04 to the tower |0| as reux, the remaining net condensate passing through pipe |20, pressure reducing valve |2| and pipe |22 into feed tank |23. The liquid aromatic-containing products formed during the gas cracking operation and collected in the distillate accumulator 68, are also passed under the pressure existing therein through pipe |24 intopipe |22 to the feed tank |23. Any light Cz hydrocarbons remaining in the liquid passing to the feed tank |23 which hydrocarbons are to be removed from the liquid may be vented Afrom the accumulator through pipe |25, valve |26, pipe ||5 and pipe 83 to the low pressure section of residue gas pipe 5.

The liquid in the feed tank |23 contains the desired aromatic-containing products of the nature of motor fuel formed-in the low pressure gas cracking and polymerization stages and is withdrawn through the pipe |21 by pump |28 and passed through pipe |28, heat exchanger |30 and pipe |3| into secondary fractionator |32. 'I'he fractionator |32 is a conventional stabilizer which may be operated at from`2'l5 lbs./sq. in. gauge to 475'lbs. /sq. in. gauge, preferably about 350 lbs./sq. in. gauge, and have suitable reboiling means |33. The bottoms discharged from the reboiler |33 are aromatic-containing products of the nature of motor fuel of 90 to 100 Octane No. CFR Motor Method stabilized as to end point and these, pass through pipe |34, heat exchanger |30, pipe |35, cooler |36, pipe |31 and pressure reducing valve |38 into pipe 38 wherein they are blended with the stabilized aromatic products of the high pressure polymerization operation and discharged from the system as the flnaiproduct.

'Ihe overhead products of the fractionator |32 are mostly C3-C4 hydrocarbon compounds which pass` through pipe |38, condenser |40 (wherein pipe |4| into reflux accumulator |42. A portion of the condensate is withdrawn from the accumulator |42 through pipe |43 by pump |44 and returned through pipe |45 to the fractionator |32 as reflux. The net condensate in the accumulator |42 ows through the pipe |46 under the existing pressure'back into the pipe I as recycle entering the system with the fresh gas.

The tar and fuel oil separated from the reaction products following each of the conversion steps and discharged into the feed pipe |9, passes through heater |41 and pipe |48`into stripping tower |49 wherein at a reduced pressure of from 10 lbs/sq. in. gauge to 50 lbs/sq. in. gauge, preferably about 25 lbs/sq. in. gauge, and by the addition of heat, the fuel oil and tar may be stripped of the lower boiling hydrocarbons and passes from the stripping tower through the pipe |50. cooler |5I, pipe |52 and pressure reducing valve |53 to storage tanks (not shown). The lower boiling hydrocarbons flow upwardly through fractionating trays (not shown) countercurrent to downowing reflux. the overhead products passing through pipe |54, condenser |55 and pipe |56 into accumulator |51. The low boiling quench condensate formed is withdrawn from the accumulator through pipe |58 by pump |59 which discharges through the pipe |60. A portion of the distillate in the pipe |60 is returned through pipe IBI and pressure control valve |62 to the tar stripper |49 as reflux.

'Ihe net `discharge from the pipe |60 passes through supply pipe |63 from which streams may be returned through pipe |64 and pressure control valve |65 to quench accumulator 60, through pipe |66 and pressure control valve |61 to distillate accumulator 23 and through pipe |69 and pressure control valve |69 to quench accumulator 82, respectively.

Although I have described my invention in connection with the conversion of gases containing a substantial proportion of olenic or unsaturated hydrocarbons, it will be understood that natural hydrocarbon gases or refinery gases of low olefin content may also be treated separately or in conjunction with gases rich in olefins. When the treatment of low olen containing gases is contemplated, these gases may be fed into the pipe 46 leading to the cracking coil 48 in order to rst crack the gases. The resulting products may be treated in the same manner as pointed out with respect to gases fed from primary fractionator 33 and line 49.

When starting with predominantly saturated gas, it is cracked in the coil 48, chilled at 5|, and the tar separated from the reaction products in 54.- -The remaining'products pass through conl denser 59 and accumulator 60 where part of the reaction products are condensed and recycled as cooling and reflux stock. The remaining uncondensed vapors and gases pass through line 64 and compressor 65 and condenser 61 to accumulator 69. 'I'he heavier fractionsl of the gas, together with the aromatic distillates, are condensed and collected in 69. The Cz compounds, which are not condensed, vare then charged through heating coil 1| and reaction coil 12 for polymerization. After separation of the tar from the polymerized reaction products, the remaining products are cooled. The condensate is used for chilling and reux stock and any excess is passed through line 86 and joined with the condensate from the cracking stage in line |24. The gases from the polymerization stage are treated with absorbent liquid in tower 89 in order to extract the remaining heavier gas fractions and light vapors therefrom. The unabsorbed gases are eliminated through line 9|. The absorbed constituents are eventually passed through line |20 to join the distillate from the cracking stage in line |20. The combined liquid fractions are passed to accumulator |23 and from there to fractionator |32. The gas from fractionator |32, which was dissolved in and separated from the liquid fractions, is recycled through line |46 to the high pressure polymerization coil |2.

While the foregoing description of my process illustrates the treatment of the Ca-Ci unsaturates in the high pressure,4 high temperature polymerization coil and the treatment of the C2 unsaturates formed by cracking or by separation from the gases entering the system, in a separate high temperature, low. pressure polymerization coil, it is to be understood that this is by. way of example only. My process comprehends broadly the treatment of the polymerizable normally gaseous oleflnes lunder polymerizing conditions of heat and pressure which are in so far as is commercially practical, establishedas most favorable to the differing reaction velocities of the respective hydrocarbons undergoing treatment.

It will be understood that certain features and sub-combinations are of utility and may be employed Without reference to other features and sub-combinations. This is contemplated by and is within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims without departing from the spirit of my invention. It is,

therefore, to be understood that my invention is not to be limited to the specic and described.

Having thus described the invention, what is claimed is:

1. The process for obtaining liquid aromatic hydrocarbons from normally gaseous olefin-containing hydrocarbons, which comprises separating said gaseous hydrocarbons into fractions of successively lower boiling range, separately heatdetails shown -ing a fraction of higher boiling range to initiate polymerization of the unsaturates present, introducing the heated fraction to a reaction zone wherein formation oi' polymers occurs, removing the products of reaction from the reaction zone, fractionally separating the Aproducts of reaction into a tar fraction, an aromatic polymer fraction and unpolymerized hydrocarbons of successively lower boiling ranges, separately heating unpolymerized hydrocarbons so separated to a temperature at which said hydrocarbons will be converted into unsaturated hydrocarbons, combining gaseous reaction products from the last mentioned conversion step with a rst mentioned fraction of lower boiling range than the fraction subjected to the aforesaid polymerization stepV separately heating the combined gas fractions to initiate polymerization of the unsaturates present, introducing the heated fractions last mentioned to a separate reaction zone wherein formation of polymers occurs, removing the products of reaction from said last mentioned zone, and fractionally separating said last mentioned products of reaction into a tar fraction,- an aromatic polymer fraction and normally gaseous hydrocarbons.

2. The process of claim 1 including recycling only the higher boiling portions of said last mentioned normally gaseous hydrocarbons to said ilrst mentioned heating step for further polymerization.

3. The process for obtainingliquid aromatic hydrocarbons from normally gaseous hydrocarbons, which comprises separating said gaseous hydrocarbons into liquid and gas fractions of successively lower boiling range, separately heating said liquid fraction at high pressureto initiate polymerization of the unsaturates present, introducing the heated fraction to a reaction zone wherein formation of polymers occurs, removing the products of reaction from the reaction zone, and quenching them to inhibit the polymerization reaction, fractionally separating the quenched products into a tar fraction, an aromatic polymer fraction and unpolymerized gas, separately heating said unpolymerized gas and a first mentioned gas fraction at a relatively low pressure to a temperature at which said fractions will be converted to form polymers and substantial quantities of unsaturated hydrocarbons, removing the products of reaction from said last mentioned heating zone, and quenching them to inhibit the cracking reaction, separating the quenched products into a tar fraction, an aromatic polymer fraction anda gas fraction containing unsaturates, separately heating said last mentioned gas fraction together with a nrst mentioned gas fraction at a relatively low pressure to initiate polymerization of the unsaturates present, introducing the heated fraction last mentioned to a separate reaction zone wherein formation of polymers occurs, removing the products of reactio'n from said last mentioned reaction zone and quenching them to inhibit the polymerization reaction, fractionally separating the quenched products into a tar fraction, an aromatic polymer fraction and unpolymerized hydrocarbon fraction of successively lower boiling ranges.

4. The process of converting normally gaseous hydrocarbons into low boiling liquid hydrocarbons which comprises subjecting said gas to conditions of time, temperature, and pressure suitable for converting saturated to unsaturated hydrocarbons, separating the reaction products into liquid and gaseous fractions, subjecting said gaseous fractions to high temperature and low pressure suitable for polymerizing unsaturated hydrocarbons to liquids, separating the reaction products from the polymerization step into liquid and gaseous fractions, combining liquid fractions from said conversion and said polymerization steps, separating dissolved gases from said combined liquids, and polymerizing separated gases at higher pressure and lower temperature vthan those to which said gaseous fractions are subjected in the rst polymerization step.

5. Process in accordance with claim 4 in which the second mentioned polymerization step is carried out at temperatures of 10501080 F. and the rst mentioned polymerization step is carried out at temperatures of 1100l200 F.

6. Method in accordance with claim 4 in which the incondensible gases from the second mentioned polymerization step are eliminated from the system.

7. 'I'he process for obtaining liquid aromatic hydrocarbons from normally gaseous hydrocarbons, which comprises separating said'gaseous hydrocarbons into fractions of successively lower boiling range, separately heating one of said 4ing within .the gasoline range, separating theV reaction products into a heavy polymer fraction,

a fraction' containing the gasoline boiling range constituents and a. gaseous' fraction, combining the last mentioned gaseous fraction with one of said rst mentioned fractions of lower boiling range, subjecting the combined fractions to conditions of time, temperature and pressure suitable for converting saturated into unsaturated hydrocarbons, separating liquid from gaseous reaction products, and subjecting the gaseous products to conditions of time, temperature and pressure in a separate reaction zone suitable for polymeriz'mg unsaturated hydrocarbonsto aromatic hydrocarbon liquids, said last mentioned temperature and pressure being respectively higher and iowen-than those to which said gaseous hydrocarbon fraction is subjected in the rst. mentioned conversion step. y

8. Process in accordance with claim 7 in which uncondensed gases from the polymerizing step are eliminated from the system and liquefied gases are recirculated to the first mentioned conversion step.

9. 'I'he process for obtaining liquid hydrocarbons from normally gaseous olen containing hydrocarbons, which comprises separating said gaseous hydrocarbons into a fraction Jcontaining chiefly C3 and C4 hydrocarbons and another fraction containing chiefly C2 and lower hydrocarbons, subjecting said Ca, C4 fraction to conditions of temperature, pressure and time in a polymerization zone suitable for converting a substantial portion of said fraction to liquid hydrocarbons boiling within the gasoline range, cooling the reaction products, separating the normally liquid from the normally gaseous constituents, subjecting said normally gaseous constituents to conditions of temperature, pressure and time, in a separate conversion zone, suitable for converting a substantial portion of said gaseous constituents to unsaturated hydrocarbons, separating the reaction products from said conversion zone into normally liquid and normally gaseous constituents, mixing said last mentioned gaseous constituents with said fraction^containing chiefly Cz and lower hydrocarbons, and subjecting the mixture to polymerization in a separate zone at temperatures higher than and pressures lower than those to which said Ca, C4 fractions are subjected.

10. Apparatus for converting hydrocarbon gases to liquid hydrocarbons comprising means for separating said gases into a higher boiling and a lower boiling fraction, means for heating said higher boiling fraction, reacting means for maintaining said heated gases under conversion conditions for a period of time suiicient to convert gaseous hydrocarbons to liquid hydrocarbons,v

means for separating reaction gases from liquids, a second heating and reacting means, means for charging said reaction gases to said second heating and through said second reacting means, means for separating liquid and gaseous reaction products produced in said second reacting means, a. third heating and reacting means, lmeans for charging gaseous products produced in said second reacting means to said third heating and through said third reacting means, andmeans for optionally charging said lower boiling fraction to said second-or said third heating means.

11. Apparatus for converting hydrocarbon gases to lliquid hydrocarbons comprising means for heating and reacting said gases, means for passing said gases through said heating and reacting means, means `for separating gas from the liquid reaction products, means for cracking gases, means for passing said separated gases through said cracking means, means for separating gases and liquids issuing from said cracking means, a second'heating and reacting means.

means for charging gases from. said cracking means to said second heating and reacting means. means for separating condensible from incon` densible products issuing from said second reacting means, means for absorbing the heavier portion of the incondensible products in a liquid absorption medium, means for separating the absorbed 'constituents'irom the absorption medium, means formixing separated constituents Vwith said condensible products, means for separating normally gaseous constituents from normally liquid constituents rin said mixture, and means for recycling separated normally gaseous constituents to said first mentioned'heating and reacting means.

HERMANN CLAUS SCHU'IT. 

